Changeable pitch airscrew hub



March 4, 1947. D. R. MacA P I 2,417,003

CHANGEABLE PITCH AmscaEw mm 2 Shets-Sheot 1 Filed Sept. 18. 1945 "I ON N. E

mg I

III

CHAN GEABLE PITCH AIRSCREW Donald R. MacAlpin, Lackawanna, N. Y., as-

signor to Bell Aircraft Corporation, Buflalo,

ipplication September 18, 1943, Serial No. 502,949

Claims. (Cl. 170-463) invention relates to air-screws, and more laz ly to adjustable blade pitch propellers rotors or all-screws such as are adaptedfor .n aircraft and the like. v

oi the objects of the invention is to problade pitch control mechanism of rugged structurally simplified and otherwise imto provide an improved mechanism having the above said features, and which permits the blade elements thereof'to be selectively adjusted in any desired manner.

said features which comprisesan interlocking proved form. Another object of the invention is Another objectis to proride a rotor or propeller embodying the above lie a propeller or rotor which embodies a hub.

shaft in may be of accordingly modified form.

Th shaft I0 carries at its outer end a hub piece l2 which comprises as illustrated in detail in Fig. 4 a body centrally apertured as at I4 so as to be pressed-fitted upon the shaft ll to be carried integrally therewith. (A locking thimble l5 (Fig. 1) is threaded lnteriorly or i the shaft III to hold the hub 121m place thereon.

structural unit having its parts so arrangedthat centrifugal force loads are carried from one blade root element oi the hub around the device providing central connection to the drive shalt and thence into the opposite blade root hub element in such manner as to provide" a complete interlocking circle of structural elements embracing the connection with the drive shaft whereby to withstand in improved manner the centrifugal forces acting upon the rotor blades. Another object of the invention is to provide a rotor or propeller arrangement em-f bodying the abovesaid features and being 01' improved simplicity and lesser number 01 opera.-

. tive parts, and of reduced overall size and weight.

Other objects and advantages of the invention.

will appear from the specification hereinafter.

In the drawings: PIE. 1 is a side elevation, partly in section, of

a rotor hub and blade pitch change mechanism of the invention;

The hub is formed with'a pair oi-dlainetrically opposed and laterally extending end portions Iii-46 which are bored in common align- I ment and in a direction normal to the aide oi the bore l4. Needle bearings l8--l8 are mounted within the bored portions iii-i8 oi the hub so as to rotatably carry corresponding pivot pins 26-20 to extend therefrom.

-A pair of generally c-shaped brackets Il-ll are arranged in relatively overlapped relationship and having their end portions mounted upon.

. saidcoaxially disposedpins 20-40 to provide,

in eifect, a loop or llnk device embracing the .hubpieCe l2 and comprising a pair of bait link brackets 30-4! whichare relatively pivotable Fig. 2 is an end view, partly in section, of the mechanism of Fig.1;

Flg. 3 is a. plan' view, partly in section, thereoi: and

Fig. 4 is a disassembled view 01 the central hub element thereof.

The invention is illustrated in the drawing as being embodied in a rotor hub and rotor blade anti-torque rotor tor use in helicopter air craft Y or the like. The rotor power supply shaft .is

designated in; and it will beum Brstood that the.

shalt ill may comprise anysultable'shaft' device.

mounted by bearings upon the aircraft structure to extend therefrom and to carry the rotor hub at the extending end portion thereof. The shaft ill is shown herein as being of tubular. formation so as to accommodate interiorly thereabout the axisoi the pins 20-20.

As shown more clearly in Fig. 2, the bracket 30 comprises a relatively large end portion 31 and a relatively small opposite end portion 34;

and the end portions of eachbracket are interj connected by a side plate portion 35. The bracket end portion 32 is bored to carry the outer race of a ball bearing as; and the bracket end portion 34 is shaped to terminate in a stub portion which fits into the inner race or a ball-bearing 38 carried by the bracket 3| in th manner of the mounting of the bearing 36 upon the bracket 80. The bearings iii-38 are of identical manuiacture in the interests of standardization of parts. Also, the brackets 303l are of identical form. Thus, the bracket 3| comprises an enlarged end portion 42 carrying the bearing 38; a reduced end portion 44 engaging the inner race of the bearing 36; and a, sid or body portion 45; all of which correspond to the portions 32-44-45 of the bracket 30. Thus, the'brack- 'ets 3ll--3I are adapted tobe oppositely arranged NlTED s'lvirss 7." rrlsirr OFFICE" The bracket small end portions are bored and tapped and screwthread mounted, as indicated at idid, upon the corresponding of the pins ib-iit; and the pins 2t-2ll are headed at it-db to hold the bearings 3t38 in assembled relation upon the brackets tt3l. Thus, it will be understood that the bearings 36-38 interconnect the corresponding small and large end portions and e l-t2 of the bracket devices so as to maintain the latter to be locked together to form in efiect a complete loop or link unit which embraces the hub 02 and comprises in effect two half link devices which are relatively plvotable about the common axis oi the pins tb-Zfl and pivotable relative to the hub piece it;

The enlarged end portions t2-t2 oi. the brackets Elie-ti may be provided with any suitable blade mounting means, such as is illustrated herein, by way of example, to comprise in each case a pair of oppositely disposed clamp plates 5b% which are detachably mounted upon the bracket devices by means of bolts 52 carrying blade mounting bolts at their outer ends so as to be adapted to engage in firmly clamped relation upon the root ends of the corresponding rotor blades. other suitable form of blade root receiving and fastening means may be employed in lieu of the specific lorm thereof illustrated and described.

Thus, it will be appreciated that the combination hub and blade mounting bracket devices described hereinabove are adapted to mount the rotor blades to extend radially from the shaft lbit will be understood, however, that any for blade pitch adjustment purposes by any sultable pilot controlled mechanism (not shown) which may be connected to the end of the pushpull member 60 which is opposite to the end thereof shown in the drawing. For example, the shaft It may be arranged to mount a driving gear on a suitably shouldered portion of the shaft as indicated at 62, whereby power may be delivered to the shaft through the gear device and whereby the adjacent end portion of the push-pull member may be extended beyond the gear for connection to any suitable pilot controlled linkage or other actuating device.

At the hub end of the shaft l0 and interiorly thereof it is fitted with a sleeve 34 carrying a ball bearing 65 which is locked in position by a nut 66 subsequent to assembly of the push-pull rod 50 within the shaft ill. The rod Ell is shouldered at $8 to be engaged thereby between a shoulder portion 89 of the sleeve E i and the bearing 65, to prevent longitudinal displacement of the rod til relative to the sleeve t l without interfering with rotation of the sleeve and shaft and hub mechanism relative to the control rod 60.

Thus, push-pull movements oi. the rod till will actuate the sleeve as to move in corresponding directions axially of the rotor hub while being free at all times to rotate therewith. At its outer end the sleeve lid carries a pair of diametrically and to be driven thereby upon rotation of the shaft while being free to turn individually in heart th -ii and tit-33 about the axes of the molmting pins for blade pitch change purposes. Also, it will be seen that all centrifugal forces due to rotation of the blades about the oi the shaft ill will be transmitted directly by the blades into the C-brackets 3El-tl and car vied by the bracket devices around the hub l2 and then into the hub in the form of compression loads thereon. Thus, the small end portions oi the brackets will dissipate the centrifugal force loads through simple abutting pressures against opposite sides of the hub 92; and all other elements of the hub mechanism including the bearings 38, 3d, and is are relieved of any duty with respect to combattlng the efiects oi centrifus gal forces, However, as illustrated in Fig. 3, the side plate portions of the brackets til-3i are preferably webbed, as at bit to stiffen the body portions of the brackets against secondary loads incidental to primary loads transmitted through the rotor blades.

Any suitablearrangement for feathering or adjusting the pitch of the rotor blades may be embodied in. combination. with the rotor hub arrangement hereinabove described. For example, one form of blade pitch change mechanism that may be effectively employed ma include a pushpullor other actuating control "device threaded through the hollow interior of the drive shaft it. In view of the) character of the hub and blade carrying bracket arrangement of the invention, as explained hereinabove, the drive shaft l0 may be tubular form and the interior thereof occupied by a blade pitch change actuating mechanism without interfering with the structural or functional arrangement of the hub mechanism. For example, as shown in the drawing the blade pitch change mechanism may comprise a push-pull member fill which is threaded through the shaft it and arranged to be longitudinally displaced opposed arms illill (Fig. 3) each of which pivotally connects by means of a pin l2 with a clevis 73. The clevis "i3 is tapped and threaded to receive one end of a corresponding adjustment screw it, the other end of the screw being similarly received within a tapped and threaded clevis it which in turn pivotally connects by means of a pin it to a horn it extending laterally from a side portion 'of the corresponding one of said O- brackets til-3i. Thus, it will be understood that simple push-pull movements of the rod 60 rela... tive to the drive shaft id will correspondingly pull or push upon the clevis-screw devices so as to simultaneously rotate the G brackets 30-38 in opposite directions about the axes of the bearings 36, 38, and 18, thereby procuring feathering or pitch adjustments of the rotor blades. The screws l ti l may be'manipulated whenever ad- ,iustment of the pitch control mechanism relative to the rotor blades is required.

Thus, the invention provides an unusually cornpact and structurally rugged; yet light-weight and smooth operating blade mounting hub and pitch change mechanism. It will be understood.

that although only one form of the invention has been shown and described in detail, it will be apparent to those skilled in the art that the invention is not so limited but that various changes may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. An airscrew device comprising a drive shaft, a hub member secured to said shaft, diametrically opposed pins iournalled in said member, a pair of brackets embracing said member, one end of each bracket beingsecuredto one of said pins, the other end preach bracket being adapted to support a blade, and thrust-bearing means interposed between the blade receiving end of each bracket and the pin receiving end of each other bracket, whereby said brackets are mutually pivotally related for adjustment about a common axis.

2. An airscrew device comprising a drive shaft, a hub member secured to said shaft, diametrically opposed pins journalled in said member, a pair oi brackets embracing said member, one end of each bracket being secured to one of said pins,

secured to one of said pins, the other end of each bracket being adapted to support a blade, and thrust bearing means interposed between the blade receiving end of each bracket and the pin receiving end of each other bracket, whereby said brackets are mutually pivotaily related for adjustment about a common axis.

4. An airscrew device comprising a drive shaft, a hub member secured to said shaft, diametrically opposed pins journalled in said member, a pair of brackets embracing said, member, one end of each bracket being secured to one of said pins, the other end of each bracket being adapted to support a blade, and thrust bearing means interposed between the blade receiving end of each bracket and the pin receiving end'of each other bracket, a laterally offset rigid connecting portion carried by each of said brackets, a push rod extending through said drive shaft and terminating beyond said hub member in a crosshead extending at right angles to said axis, and link means pivotaiiy connecting the opposite ends of said crosshead and said laterally offset rigid connecting portions, whereby movement of said push rod axially of said drive shaft imparts arcuate movement to said brackets.

5. An airscrew device comprising a drive shaft, a hub member secured to said shaft, diametrical- 1y opposed pins journalled in said member, a pair of brackets embracing said member, one end of each bracket being secured to one of said pins, the other end of each bracket being adapted to support a blade, and thrust bearing means interposed between the blade receiving end of each bracket and the pin receiving end of each other bracket, a laterally offset rigid connecting portion carried by each of said brackets, a crosshead extending at right angles to said axis, a push rod extending through said drive shaft and terminating beyond said hub member in antifriction bearing engagement in said crosshead, said crosshead being fixed for joint axial movement with said push rod, and link means pivotaliy connecting the opposite ends of said crosshead and said laterally offset rigid connecting portions, whereby axial movement of said push rod imparts arcuate movement to said brackets. I DONALD R. MACALPIN.

REFERENCES or'rnn The following references are of record in the file of this patent:

UNITED STATES PATENTS 

